In a recent study by Angleró-Rodríguez et al. (2016) in the journal Science Reports showed that a tripartite interaction involving two microbes – the fungus Penicillium chrysogenum, and the protozoan Plasmodium falciparum – and the mosquito, Anopheles gambiae, leads to an increased susceptibility of the mosquito the the malaria parasite, P. falciparum, in the presence of the fungus. The fungus does not appear to affect the survival of A. gambiae in a significant way, however, it does increase the number of oocysts in the midgut of the mosquito, which could lead to an increased rate of malarial transmission.
The results of this study strongly suggest that the mechanism involved in this interaction is governed by the sequestration of the amino acid L-arginine by conversion of L-arginine to L-ornithine by the enzyme ornithine decarboxylase. When L-arginine is not available (sequestered), it is unable to be used by other enzymes to produce nitric oxide (NO). In other studies, nitric oxide was shown to aid in the killing of P. falciparum oocysts in mosquitoes (Luckhart et al. 1998) and the same mechanism seems to be at play in this interaction as well. To read the article for yourself, follow the link here.
Angleró-Rodríguez et al. (2016) A natural Anopheles-associated Penicillium chrysogenum enhances mosquito susceptibility to Plasmodium infection. Scientific Reports 6:34084.
Luckhart et al. (1998) The mosquito Anopheles stephensi limits malaria parasite development with inducible synthesis of nitric oxide. PNAS. 95(10):5700-5705.10.11.16